First, get the right costume. Look for a bright yellow Pikachu onesie or make one yourself with yellow fabric and black accents for the ears, tail, and markings. Then, focus on the face. You can use yellow face paint to complete the look. Don't forget about Pikachu's rosy cheeks, which can be added with a bit of pink blush. Also, practice Pikachu's cute poses and expressions, like its shocked face or its happy hopping pose. This will make your cosplay more engaging and fun.
If the cosplayer traveled through the anime novels that they cosplayed, they might find some unexpected plots. For example, they might encounter their own characters and communicate with them. Or they might discover that something different was happening to their characters than they knew. In short, this kind of plot might surprise and excite them.
A simple Nezuko and Zenitsu fanfiction could be that they go on a journey together. Along the way, they encounter other demon slayers who are initially skeptical of Nezuko. But Zenitsu stands up for her, explaining that she's different. This shows the depth of their friendship and how Zenitsu has come to trust Nezuko completely.
One common theme is self - discovery. Since Zenitsu has a complex personality, many fanfics focus on him finding out more about himself, his powers, and his place in the world. Another theme is friendship. He often forms strong bonds with other characters in fanfics, like Tanjiro and Inosuke.